This page explains how to create an assessment to allow your backend to verify the authenticity of the token that reCAPTCHA sends. reCAPTCHA sends an encrypted response, the reCAPTCHA response token (also known as token), when the end user triggers an HTML action.
For any type of reCAPTCHA key integration (checkbox or score), you must create
an assessment to assess the results of execute()
in your backend by submitting the generated token to
the assessment endpoint.
reCAPTCHA processes the
submitted token and reports the token's validity and score.
The first 10,000 reCAPTCHA monthly assessments are free. To continue creating assessments after you reach the free monthly usage limit (10,000 assessments per month), you must enable billing for your Google Cloud project. For more information about billing for reCAPTCHA, see Billing information.
Before you begin
- Prepare your environment for reCAPTCHA.
- Ensure that you have the following Identity and Access Management role:
reCAPTCHA Enterprise Agent (
roles/recaptchaenterprise.agent
). - Install score-based keys or checkbox keys on your website.
-
Set up authentication to reCAPTCHA.
The authentication method you choose depends on the environment where reCAPTCHA is set up. The following table helps you choose the appropriate authentication method and the supported interface to set up authentication:
Environment Interface Authentication method Google Cloud - REST
- Client libraries
Use attached service accounts. On-premises or a different cloud provider REST Use API keys or Workload identity federation. If you want to use API keys, then we recommend securing the API keys by applying API key restrictions.
Client libraries Use the following:
- For Python or Java, use API keys or Workload identity federation.
If you want to use API keys, then we recommend securing the API keys by applying API key restrictions.
- For other languages, use Workload identity federation.
Retrieve a token
Retrieve a token from web pages in one of the following ways:
- The resolved value of the promise returned by the call to
grecaptcha.enterprise.execute()
. - Use the
g-recaptcha-response
POST parameter when a user submits a form on your site. - As a string argument to your callback function if
data-callback
is specified in either theg-recaptcha
HTML tag attribute or the callback parameter in thegrecaptcha.enterprise.render
method.
You can access each user's token only once.
If you need to assess a subsequent action that a user takes on your site, or
if a token expires before an assessment is created, you must call execute()
again to generate a new token.
Create an assessment
After you set up authentication, create an assessment by sending a request to the reCAPTCHA Enterprise API or by using the reCAPTCHA Client Libraries.
To improve detection, we recommend that you pass the following additional values when creating assessments:
userAgent
: The user agent is included in the HTTP request in the request header. For more information, see Learn about theUser-Agent
request header in the Mozilla Developer Network documentation.userIpAddress
: The IP address of the user sending a request to your backend is available in the HTTP request. If you use a proxy server, the IP address is available in theX-Forwarded-For
request header. For more information about getting the IP address, seeX-Forwarded-For
.ja3
: JA3 is an open source method for fingerprinting TLS clients. For more information about using JA3 to create a TLS fingerprint see the JA3 documentation, .
This helps in protecting your website and mobile applications against advanced attack patterns and human-led abuse.
The way you create an assessment is the same for score-based and checkbox keys.
REST API
Create an assessment by sending a request to the reCAPTCHA API. You can use either the gcloud CLI or API key for authentication.
Use the gcloud CLI
Create an assessment using the projects.assessments.create
method. Send this request to the v1
API endpoint.
Before using any of the request data, make the following replacements:
- PROJECT_ID: your Google Cloud project ID
- TOKEN: token returned from the
grecaptcha.enterprise.execute()
call - KEY_ID: the reCAPTCHA key associated with the site or app. For more information, see reCAPTCHA keys.
- USER_AGENT: the user agent in the request from the user's device.
- USER_IP_ADDRESS: the IP address in the request from the user's device.
- JA3: JA3 fingerprint for the SSL client. We recommend using salesforce/ja3 for computing JA3.
- USER_ACTION: the user-initiated action that you specified for
action
in thegrecaptcha.enterprise.execute()
call, such aslogin
.For more information, see Action names.
HTTP method and URL:
POST https://recaptchaenterprise.googleapis.com/v1/projects/PROJECT_ID/assessments
Request JSON body:
{ "event": { "token": "TOKEN", "siteKey": "KEY_ID", "userAgent": "USER_AGENT", "userIpAddress": "USER_IP_ADDRESS", "ja3": "JA3", "expectedAction": "USER_ACTION" } }
To send your request, choose one of these options:
curl
Save the request body in a file named request.json
,
and execute the following command:
curl -X POST \
-H "Authorization: Bearer $(gcloud auth print-access-token)" \
-H "Content-Type: application/json; charset=utf-8" \
-d @request.json \
"https://recaptchaenterprise.googleapis.com/v1/projects/PROJECT_ID/assessments"
PowerShell
Save the request body in a file named request.json
,
and execute the following command:
$cred = gcloud auth print-access-token
$headers = @{ "Authorization" = "Bearer $cred" }
Invoke-WebRequest `
-Method POST `
-Headers $headers `
-ContentType: "application/json; charset=utf-8" `
-InFile request.json `
-Uri "https://recaptchaenterprise.googleapis.com/v1/projects/PROJECT_ID/assessments" | Select-Object -Expand Content
You should receive a JSON response similar to the following:
{ "tokenProperties": { "valid": true, "hostname": "www.google.com", "action": "homepage", "createTime": "2019-03-28T12:24:17.894Z" }, "riskAnalysis": { "score": 0.1, "reasons": ["AUTOMATION"] }, "event": { "token": "TOKEN", "siteKey": "KEY_ID", "userAgent": "USER_AGENT", "userIpAddress": "USER_IP_ADDRESS", "ja3": "JA3", "expectedAction": "USER_ACTION" }, "name": "projects/PROJECT_NUMBER/assessments/b6ac310000000000" }
We recommend using any JSON parsers in the non-strict parsing mode to prevent any outages if any additional fields are introduced to the JSON response.
Use an API key
Create an assessment using the projects.assessments.create
method. Send this request to the v1
API endpoint.
Before using any of the request data, make the following replacements:
- API_KEY: API key associated with the current project
- PROJECT_ID: your Google Cloud project ID
- TOKEN: token returned from the
grecaptcha.enterprise.execute()
call - KEY_ID: the reCAPTCHA key associated with the site or app. For more information, see reCAPTCHA keys.
- USER_AGENT: the user agent in the request from the user's device.
- USER_IP_ADDRESS: the IP address in the request from the user's device.
- JA3: JA3 fingerprint for the SSL client. We recommend using salesforce/ja3 for computing JA3.
- USER_ACTION: the user-initiated action that you specified for
action
in thegrecaptcha.enterprise.execute()
call, such aslogin
.For more information, see Action names.
HTTP method and URL:
POST https://recaptchaenterprise.googleapis.com/v1/projects/PROJECT_ID/assessments?key=API_KEY
Request JSON body:
{ "event": { "token": "TOKEN", "siteKey": "KEY_ID", "userAgent": "USER_AGENT", "userIpAddress": "USER_IP_ADDRESS", "ja3": "JA3", "expectedAction": "USER_ACTION" } }
To send your request, choose one of these options:
curl
Save the request body in a file named request.json
,
and execute the following command:
curl -X POST \
-H "Content-Type: application/json; charset=utf-8" \
-d @request.json \
"https://recaptchaenterprise.googleapis.com/v1/projects/PROJECT_ID/assessments?key=API_KEY"
PowerShell
Save the request body in a file named request.json
,
and execute the following command:
$headers = @{ }
Invoke-WebRequest `
-Method POST `
-Headers $headers `
-ContentType: "application/json; charset=utf-8" `
-InFile request.json `
-Uri "https://recaptchaenterprise.googleapis.com/v1/projects/PROJECT_ID/assessments?key=API_KEY" | Select-Object -Expand Content
You should receive a JSON response similar to the following:
{ "tokenProperties": { "valid": true, "hostname": "www.google.com", "action": "homepage", "createTime": "2019-03-28T12:24:17.894Z" }, "riskAnalysis": { "score": 0.1, "reasons": ["AUTOMATION"] }, "event": { "token": "TOKEN", "siteKey": "KEY_ID", "userAgent": "USER_AGENT", "userIpAddress": "USER_IP_ADDRESS", "ja3": "JA3", "expectedAction": "USER_ACTION" }, "name": "projects/PROJECT_NUMBER/assessments/b6ac310000000000" }
We recommend using any JSON parsers in the non-strict parsing mode to prevent any outages if any additional fields are introduced to the JSON response.
C#
using System; using Google.Api.Gax.ResourceNames; using Google.Cloud.RecaptchaEnterprise.V1; public class CreateAssessmentSample { // Create an assessment to analyze the risk of a UI action. // projectID: Google Cloud project ID. // recaptchaKey: reCAPTCHA key obtained by registering a domain or an app to use reCAPTCHA Enterprise. // token: The token obtained from the client on passing the recaptchaKey. // recaptchaAction: Action name corresponding to the token. public void createAssessment(string projectID = "project-id", string recaptchaKey = "recaptcha-key", string token = "action-token", string recaptchaAction = "action-name") { // Create the client. // TODO: To avoid memory issues, move this client generation outside // of this example, and cache it (recommended) or call client.close() // before exiting this method. RecaptchaEnterpriseServiceClient client = RecaptchaEnterpriseServiceClient.Create(); ProjectName projectName = new ProjectName(projectID); // Build the assessment request. CreateAssessmentRequest createAssessmentRequest = new CreateAssessmentRequest() { Assessment = new Assessment() { // Set the properties of the event to be tracked. Event = new Event() { SiteKey = recaptchaKey, Token = token, ExpectedAction = recaptchaAction }, }, ParentAsProjectName = projectName }; Assessment response = client.CreateAssessment(createAssessmentRequest); // Check if the token is valid. if (response.TokenProperties.Valid == false) { System.Console.WriteLine("The CreateAssessment call failed because the token was: " + response.TokenProperties.InvalidReason.ToString()); return; } // Check if the expected action was executed. if (response.TokenProperties.Action != recaptchaAction) { System.Console.WriteLine("The action attribute in reCAPTCHA tag is: " + response.TokenProperties.Action.ToString()); System.Console.WriteLine("The action attribute in the reCAPTCHA tag does not " + "match the action you are expecting to score"); return; } // Get the risk score and the reasons. // For more information on interpreting the assessment, // see: https://cloud.google.com/recaptcha/docs/interpret-assessment System.Console.WriteLine("The reCAPTCHA score is: " + ((decimal)response.RiskAnalysis.Score)); foreach (RiskAnalysis.Types.ClassificationReason reason in response.RiskAnalysis.Reasons) { System.Console.WriteLine(reason.ToString()); } } public static void Main(string[] args) { new CreateAssessmentSample().createAssessment(); } }
Go
import ( "context" "fmt" recaptcha "cloud.google.com/go/recaptchaenterprise/v2/apiv1" recaptchapb "cloud.google.com/go/recaptchaenterprise/v2/apiv1/recaptchaenterprisepb" ) func main() { // TODO(developer): Replace these variables before running the sample. projectID := "project-id" recaptchaKey := "recaptcha-key" token := "action-token" recaptchaAction := "action-name" createAssessment(projectID, recaptchaKey, token, recaptchaAction) } /** * Create an assessment to analyze the risk of a UI action. * * @param projectID: Google Cloud project ID * @param recaptchaKey: reCAPTCHA key obtained by registering a domain or an app to use the services of reCAPTCHA Enterprise. * @param token: The token obtained from the client on passing the recaptchaKey. * @param recaptchaAction: Action name corresponding to the token. */ func createAssessment(projectID string, recaptchaKey string, token string, recaptchaAction string) { // Create the recaptcha client. // TODO: To avoid memory issues, move this client generation outside // of this example, and cache it (recommended) or call client.close() // before exiting this method. ctx := context.Background() client, err := recaptcha.NewClient(ctx) if err != nil { fmt.Printf("Error creating reCAPTCHA client\n") } defer client.Close() // Set the properties of the event to be tracked. event := &recaptchapb.Event{ Token: token, SiteKey: recaptchaKey, } assessment := &recaptchapb.Assessment{ Event: event, } // Build the assessment request. request := &recaptchapb.CreateAssessmentRequest{ Assessment: assessment, Parent: fmt.Sprintf("projects/%s", projectID), } response, err := client.CreateAssessment( ctx, request) if err != nil { fmt.Printf("%v", err.Error()) } // Check if the token is valid. if response.TokenProperties.Valid == false { fmt.Printf("The CreateAssessment() call failed because the token"+ " was invalid for the following reasons: %v", response.TokenProperties.InvalidReason) return } // Check if the expected action was executed. if response.TokenProperties.Action == recaptchaAction { // Get the risk score and the reason(s). // For more information on interpreting the assessment, // see: https://cloud.google.com/recaptcha/docs/interpret-assessment fmt.Printf("The reCAPTCHA score for this token is: %v", response.RiskAnalysis.Score) for _,reason := range response.RiskAnalysis.Reasons { fmt.Printf(reason.String()+"\n") } return } fmt.Printf("The action attribute in your reCAPTCHA tag does " + "not match the action you are expecting to score") }
Java
Node.js
const {RecaptchaEnterpriseServiceClient} = require('@google-cloud/recaptcha-enterprise'); /** * Create an assessment to analyze the risk of a UI action. Note that * this example does set error boundaries and returns `null` for * exceptions. * * projectID: Google Cloud project ID * recaptchaKey: reCAPTCHA key obtained by registering a domain or an app to use the services of reCAPTCHA Enterprise. * token: The token obtained from the client on passing the recaptchaKey. * recaptchaAction: Action name corresponding to the token. * userIpAddress: The IP address of the user sending a request to your backend is available in the HTTP request. * userAgent: The user agent is included in the HTTP request in the request header. * ja3: JA3 associated with the request. */ async function createAssessment({ projectID = "your-project-id", recaptchaKey = "your-recaptcha-key", token = "action-token", recaptchaAction = "action-name", userIpAddress = "user-ip-address", userAgent = "user-agent", ja3 = "ja3" }) { // Create the reCAPTCHA client & set the project path. There are multiple // ways to authenticate your client. For more information see: // https://cloud.google.com/docs/authentication // TODO: To avoid memory issues, move this client generation outside // of this example, and cache it (recommended) or call client.close() // before exiting this method. const client = new RecaptchaEnterpriseServiceClient(); const projectPath = client.projectPath(projectID); // Build the assessment request. const request = ({ assessment: { event: { token: token, siteKey: recaptchaKey, userIpAddress: userIpAddress, userAgent: userAgent, ja3: ja3, }, }, parent: projectPath, }); // client.createAssessment() can return a Promise or take a Callback const [ response ] = await client.createAssessment(request); // Check if the token is valid. if (!response.tokenProperties.valid) { console.log("The CreateAssessment call failed because the token was: " + response.tokenProperties.invalidReason); return null; } // Check if the expected action was executed. // The `action` property is set by user client in the // grecaptcha.enterprise.execute() method. if (response.tokenProperties.action === recaptchaAction) { // Get the risk score and the reason(s). // For more information on interpreting the assessment, // see: https://cloud.google.com/recaptcha/docs/interpret-assessment console.log("The reCAPTCHA score is: " + response.riskAnalysis.score); response.riskAnalysis.reasons.forEach((reason) => { console.log(reason); }); return response.riskAnalysis.score; } else { console.log("The action attribute in your reCAPTCHA tag " + "does not match the action you are expecting to score"); return null; } }
PHP
<?php // Include Google Cloud dependencies using Composer // composer require google/cloud-recaptcha-enterprise require 'vendor/autoload.php'; use Google\Cloud\RecaptchaEnterprise\V1\RecaptchaEnterpriseServiceClient; use Google\Cloud\RecaptchaEnterprise\V1\Event; use Google\Cloud\RecaptchaEnterprise\V1\Assessment; use Google\Cloud\RecaptchaEnterprise\V1\TokenProperties\InvalidReason; /** * Create an assessment to analyze the risk of a UI action. * @param string $siteKey The key ID for the reCAPTCHA key (See https://cloud.google.com/recaptcha/docs/create-key) * @param string $token The user's response token for which you want to receive a reCAPTCHA score. (See https://cloud.google.com/recaptcha/docs/create-assessment#retrieve_token) * @param string $project Your Google Cloud project ID */ function create_assessment( string $siteKey, string $token, string $project ): void { // TODO: To avoid memory issues, move this client generation outside // of this example, and cache it (recommended) or call client.close() // before exiting this method. $client = new RecaptchaEnterpriseServiceClient(); $projectName = $client->projectName($project); $event = (new Event()) ->setSiteKey($siteKey) ->setToken($token); $assessment = (new Assessment()) ->setEvent($event); try { $response = $client->createAssessment( $projectName, $assessment ); // You can use the score only if the assessment is valid, // In case of failures like re-submitting the same token, getValid() will return false if ($response->getTokenProperties()->getValid() == false) { printf('The CreateAssessment() call failed because the token was invalid for the following reason: '); printf(InvalidReason::name($response->getTokenProperties()->getInvalidReason())); } else { printf('The score for the protection action is:'); printf($response->getRiskAnalysis()->getScore()); // Optional: You can use the following methods to get more data about the token // Action name provided at token generation. // printf($response->getTokenProperties()->getAction() . PHP_EOL); // The timestamp corresponding to the generation of the token. // printf($response->getTokenProperties()->getCreateTime()->getSeconds() . PHP_EOL); // The hostname of the page on which the token was generated. // printf($response->getTokenProperties()->getHostname() . PHP_EOL); } } catch (exception $e) { printf('CreateAssessment() call failed with the following error: '); printf($e); } } // TODO(Developer): Replace the following before running the sample create_assessment( 'YOUR_RECAPTCHA_KEY', 'YOUR_USER_RESPONSE_TOKEN', 'YOUR_GOOGLE_CLOUD_PROJECT_ID' ); ?>
Python
Ruby
What's next
- Interpret an assessment and take an appropriate action for your site based on the score.